1. Field of the Invention
The present invention relates generally to the field of security devices for buildings, and particularly for homes. More specifically the present invention relates to a door or window lock including a bolt receiving housing containing an alarm circuit and a conventional bolt assembly which advances a bolt into and retracts the bolt from the housing with the turn of a knob or a key. For one embodiment, the bolt receiving housing is a metal box fitted into a recess in a door frame. The box has a box forward wall with a bolt receiving opening, box side walls and a box rearward wall through which a lever switch is mounted so that the switch lever extends forwardly into the box. The box is sized in depth relative to the throw and position of the bolt so that the thrown bolt extends into the box to an extent that it is laterally adjacent to the switch lever. The remainder of the switch extends rearwardly from the rear wall of the box into an electrical raceway in the building wall.
When the bolt is thrown to lock the door or window, movement of the door or window toward an open position drives the bolt laterally against the switch lever and thereupon pivots the lever to throw the switch and complete the alarm circuit to cause the alarm to sound. Thus the alarm is sounded while the bolt remains intact and in advance of intruder entry into the building. To shut off the alarm, the building owner simply unlocks the bolt, reaches into the housing with a finger or a tool, and throws the switch lever back into the deactivation position.
2. Description of the Prior Art
There have long been bolts and alarms for inhibiting intruder entry into buildings. These have in some instances been combined mechanisms in which breaking or lateral movement of the bolt triggers the alarm. A problem with these latter prior devices has been that generally they do not operate in concert with the conventional bolt assembly many people have on their doors, which are conveniently operated with house keys. In these instances the alarm must be set, neutralized and deactivated in a separate operation from simply locking and unlocking the door, thus discouraging hurried people from using their alarm systems all of the time. Alternatively, in the few instances in which a generally conventional bolt assembly is used, deactivation of a triggered alarm can be complicated and difficult.
One such prior device is that of Makishima, U.S. Pat. No. 2,660,632, issued on Nov. 24, 1953. Makishima discloses a burglar alarm safety lock using an apparently conventional bolt, having a bolt receptacle including a button switch which activates the alarm when depressed. The switch button is positioned at the side of the extended bolt toward which the bolt would move upon opening the door. A cantilever-mounted tab extends between the bolt and the button, so that when sufficient pressure is exerted against the door, the bolt bends the tab against the button and the tab remains bent so that the button remains pressed and the alarm remains activated. A problem with Makishima is that deactivating the alarm requires bending the tab back out of contact with the switch button, which is awkward in part because the tab is contained within the bolt receptacle.
Queren, U.S. Pat. No. 4,390,867, issued on Jun. 28, 1983, teaches a burglar alarm system. Queren reveals another bolt and bolt receptacle arrangement in which attempting to open the door causes lateral movement of the bolt against a plate which bends the plate to cause electrical contact with a screw which completes the alarm circuit. As in Makishima, the bent plate often must be bent back to its original position to deactivate the alarm.
Maged, U.S. Pat. No. 3,851,325, issued on Nov. 26, 1974, teaches a combined lock and alarm apparatus. Maged includes a bolt assembly for mounting on the door and a bolt receiving structure for mounting on the door frame. The alarm circuit is contained within the bolt assembly housing and includes spaced apart electrical contacts. A bolt slide stem extends laterally from the bolt out of the bolt assembly housing through a stem slot. The alarm circuit includes a sound generator wired to a power source and a pair of spring-biased electrical contacts placed within the sliding path of the stem. The bolt is spring-biased outwardly toward the door frame. The bolt receiving structure includes a guide flange against which the biased bolt rests, and along which the bolt slides if the door is pushed in a door opening direction while the bolt is thrown. Movement of the bolt beyond the guide flange permits the bolt to extend further into the bolt receptacle, so that the stem rides against and presses the electrical contacts together to sound the alarm. A problem with Maged is that no provision apparently is made for use of an ordinary bolt assembly with its household key. The bolt as illustrated must be operated from within the building by moving the bolt stem. Bobrowski, et al., U.S. Pat. No. 3,755,802, issued on Aug. 28, 1973 teaches a similar bolt assembly containing an alarm circuit.
Engstrom, et al., U.S. Pat. No. 4,587,517, issued on May 6, 1986, reveals an intrusion sensing device. Engstrom, et al., provides a bolt and a bolt receptacle having a bolt receiving opening surrounded by a paper and adhesive layer. The layer contains a conductor segment of an alarm circuit made of a frangible material such as conductive ink. Applying pressure to open the door from a closed position without retraction of the bolt transmits force to strike plate fasteners causing a slight displacement of the strike plate, in turn causing the surface of the frame surrounding the fasteners to fracture. The conductor segment in the paper and adhesive layer breaks as a result, sounding the alarm. Problems with Engstrom, et al. are that the broken conductive material must be replaced after activation, and the alarm does not sound until the door frame is already damaged and perhaps entirely broken.
Mickel, U.S. Pat. No. 4,912,456, issued on Mar. 27, 1990, discloses a door latch alarm. Mickel includes a housing including first and second compartments. The lower first compartment wherein the first compartment includes a dead-bolt latch and a secondary bolt integrally formed with a first switch projecting through a slot communicating from the first to the second compartment. The first switch, upon retraction of the secondary bolt, completes an electrical circuit to activate an audible alarm. A second switch is directed outwardly of the second compartment to deactivate the circuit. The problems of Maged are once again presented.
Albert, U.S. Pat. No. 3,978,467, issued on Aug. 31, 1976, discloses a door alarm system responsive to forced entry. Albert includes a contact plate attached to a door frame spaced apart from the latch plate. The two plates are electrically insulated from each other and mounted so that the latch plate moves if any attempt is made to force the door latch. The two plates are connected to a circuit, the circuit including a contact relay and a thermal relay. When the two plates contact each other, no matter how instantaneously, the contact relay is energized. The alarm circuit is maintained until a certain amount of time has elapsed. A problem with Albert is that complex circuitry is required, and because of its complexity this circuitry is more likely to malfunction.
It is thus an object of the present invention to provide a door and window securing combined alarm and bolt apparatus which simultaneously locks the door or window and sets an alarm against unauthorized entry.
It is another object of the present invention to provide such an apparatus which permits partial opening of the door or window before the bolt abuts a stop to prevent further movement, sounding the alarm during this interval, so that the alarm sounds prior to intruder entry, giving building occupants and police greater response time.
It is finally an object of the present invention to provide such an apparatus which is strong, simple, reliable and relatively inexpensive to manufacture.